Install Optifine if you are using it (Remember that Optifine Light isn’t compatible with Minecraft Forge, which means this mod won’t work with Optifine Light either. Optifine Ultra and Optifine Standard work fine with Minecraft Forge)

If ‘coremods’ folder does not exist, either create a new folder named ‘coremods’ in ‘.minecraft’ folder or start Minecraft with Minecraft Forge installed, and put the jar file in the newly-generated ‘coremods’ folder.